1. Technical Field
The present disclosure relates to a fuel cell and a fuel cell system.
2. Description of Related Art
A solid polymer electrolyte fuel cell includes a membrane electrode assembly in which a catalyst electrode layer is disposed on both surfaces of an electrolyte membrane having proton conductivity. In the membrane electrode assembly, an electrochemical reaction progresses, which produces water. Therefore, water is present in the fuel cell. In a case where the fuel cell operates for a long period of time, cationic impurities included in in-take air may be incorporated into water in the fuel cell, or cationic impurities included in materials constituting the electrolyte membrane and the catalyst electrode layer may be eluted into water in the fuel cell. As a result, the power generation performance deteriorates. Therefore, a method of restoring power generation performance in which the amount of cationic impurities is reduced by operating a fuel cell at a high load, by reversing a direction of a current drawn from a fuel cell, or cleaning the inside of a fuel cell with a cleaning solution is known (for example, Japanese Patent Application Publication No. 2001-85037 (JP 2001-85037 A)).
However, in a state where a fuel cell is mounted on a fuel cell vehicle or the like, it is difficult to reverse a direction of a current drawn from the fuel cell or to clean the inside of a fuel cell with a cleaning solution. In addition, in the method of operating a fuel cell at a high load to restore power generation performance, a large amount of water is produced due to the operation of the fuel cell at a high load such that cationic impurities are exhausted to the outside of the fuel cell together with the produced water, thereby restoring the power generation performance. However, in order to maintain an appropriate amount of water in a membrane electrode assembly, a water-repellent layer may be provided on a side surface of the membrane electrode assembly. In this case, even in a case where a large amount of water is produced by operating a fuel cell at a high load, the produced water in the membrane electrode assembly is blocked by the water-repellent layer. Therefore, it is difficult to exhaust the produced water in the form of liquid, and even when a portion of the produced water is exhausted to the outside of the fuel cell, the amount of cationic impurities exhausted together with the produced water is small.